When prosperity leads to decay, misfortune. The image is of a city wall collapsing back into its own moat. In times of collapse, it helps no one to fight against overwhelming odds. Individual moral force is called for instead of violence.
In times of peace, necessary defenses can erode. The city becomes vulnerable to attack. Try not to be like the citizens who, by becoming lazy and indifferent, put their homes at risk. Be prepared for external problems, friend. Do not allow yourself to become complacent.
